1. Field of the Invention
The present disclosure relates to a cooler for cooling electronic parts and can be preferably used, particularly, as a cooler for cooling electronic parts of a double-sided cooling type in an inverter for a hybrid electric vehicle. More particularly, the present invention relates to a cooler of a built-up type for cooling an electronic part from both sides thereof.
2. Description of the Related Art
Conventionally, a known semiconductor module (an electronic part) is attached to a cooler of a water-cooling type for cooling. A semiconductor device of a double-sided cooling type is proposed in Patent document 1. The device described in Patent document 1 has a configuration in which tubes having a cooling water passage and semiconductor modules of a double-sided cooling type are piled alternately and a pressing force is applied in the direction of built-up of the tubes to hold the semiconductor modules between the tubes. Neighboring tubes and coupled to each other by bellows (coupling means) arranged between the neighboring tubes and by communication holes for making the cooling water passages and the insides of the bellows communicate with each other are formed in respective tubes. In Patent document 1, many examples are described in which the semiconductor module and the tube are brought into close contact with each other even if there are variations in the interval between tubes and in the thickness of the semiconductor modules.
If one of the examples (hereinafter, referred to as a first conventional device), neighboring tubes are coupled to each other by a bellows-shaped elastic cylinder sections and the elastic cylinder sections extend and contract in accordance with the interval between the tubes or the thicknesses of the semiconductor modules.
In another example (hereinafter, referred to as a second conventional device), a flange-shaped cylinder section with low rigidity is provided in the tube and the flange-shaped cylinder section is made to deform in accordance with the interval between the tubes or the thickness of the semiconductor modules.
In still another example (hereinafter, referred to as a third conventional device), the tube is made thinner to have lower rigidity and the tube itself is made to deform in accordance with the interval between tubes or the thickness of the semiconductor module.
Conventionally, a cooler of a built-up type 2009 is known, in which a plurality of cooling tubes 2092 are arranged in layers so as to sandwich and hold an electronic part 2004 from both sides thereof and which cools the electronic part 2004 from both sides thereof, as shown in FIG. 39 (refer to Patent document 2).
The cooler of a built-up type 2009 comprises a supply header 2094 for supplying a cooling medium to the cooling tubes 2092 and a discharge header 2095 for discharging the cooling medium from the cooling tubes 2092. One end of each of the plurality of the cooling tubes 2092 arranged in layers is connected to the supply header 2094 and the other end is connected to the discharge header 2095.
However, in the conventional cooler of a built-up type 2009, the cooling tubes 2092 are connected to the supply header 2094 and the discharge header 2095, both being made of a member different from that of the cooling tubes 2092. Because of this, there is the possibility that the manufacture of the cooler of a built-up type 2009 requires a large number of parts and, therefore, the manufacturing cost thereof is high.
Moreover, in the cooler of a built-up type 2009, the plurality of the cooling tubes 2092 are fixed to the supply header 2094 and the discharge header 2095 and, therefore, it is difficult to change the intervals between the plurality of the cooling tubes 2092. Because of this, it becomes difficult to insert the electronic part 2004 between the cooling tubes 2092 so as to bring the cooling pipes 2092 into close contact with both main surfaces of the electronic part 2004 without fail.
On the other hand, a cooler of a built-up type 2090 is known, which is configured in such a manner that a plurality of the cooling tubes 2092 are arranged so as to sandwich and hold an electronic part 2004 from both sides and, at the same time, a plurality of the cooling tubes 2092 are made to connect with each other via connecting pipe 2093 so that a cooling medium can flow to each cooling tube 2092, as shown in FIG. 40 (refer to Patent document 1).
However, in this cooler of a built-up type 2090 also, it is necessary to join the connecting pipe 2093, which are made of a member different from that of the cooling tubes 2092, to the cooling tubes 2092 to assemble the cooler of a built-up type 2090. Because of this, a problem arises in that the manufacturing cost is high and, at the same time, the productivity is difficult to improve.
[Patent document 1] Japanese Unexamined Patent Publication (Kokai) No. 2002-26215
[Patent document 2] Japanese Unexamined Patent Publication (Kokai) No. 2001-320005
However, as in the device described in Patent document 1, when a tube is manufactured by extrusion, inner walls 2001x are formed on the inside of the tube 2001 in order to accelerate heat exchange and to ensure the strength thereof, and the inner walls 2001x exist in the entire area in the direction of extrusion, as shown in FIG. 38. In addition, after extrusion, it is necessary to remove the inner wall 2001x of the tube 2001 at the portion where the tube 2001 and a bellows are joined, that is, at the portion where a connection hole 2011 is formed. Therefore, this process raises the cost. Moreover, the extruded tube 1 requires side caps and this also raises the cost.
Moreover, the first conventional device and the second conventional device require the elastic cylinder sections or the flange-shaped cylinder sections, the number of which corresponding to the number of piled layers of the tubes and, therefore, a problem arises in that the number of parts of a product is increased.
In the third conventional device, as the tube is deformed in an arc shape, it is not possible for the tube to completely come into close contact with the surface of the semiconductor module and a problem arises in that the contact area between two decreases. Moreover, the third conventional device brings about a problem in that, when the tube deforms, stress tend to concentrate on the joined parts between the tubes and the header tanks.